Grinder with loss of control detection

A power tool comprising:

• a housing;
• a battery pack interface configured to receive a rechargeable battery pack;
• a motor positioned within the housing and powered via the rechargeable battery pack;
• an output shaft driven by the motor, the output shaft configured to be coupled to an accessory for operation thereof;
• a sensing circuit configured to detect, during operation of the power tool, a first rotational velocity of the power tool around a first axis, a second rotational velocity of the power tool around a second axis, and a third rotational velocity of the power tool around a third axis;
• and
• a controller configured to perform a loss of control check on the power tool by:
• receiving one or more signals from the sensing circuit representing the first rotational velocity, the second rotational velocity, and the third rotational velocity;
• applying a first sensitivity value to the first rotational velocity, a second sensitivity value to the second rotational velocity, and a third sensitivity value to the third rotational velocity to obtain a first adjusted rotational velocity, a second adjusted rotational velocity, and a third adjusted rotational velocity;
• summing a square of the first adjusted rotational velocity, a square of the second adjusted rotational velocity, and a square of the third adjusted rotational velocity;
• comparing the sum to a predetermined threshold, and
• tripping loss of control functionality based on whether the sum exceeds the predetermined threshold.

A power tool comprising:

• a housing;
• a battery pack interface configured to receive a rechargeable battery pack;
• a motor positioned within the housing and powered via the rechargeable battery pack;
• an output shaft driven by the motor, the output shaft configured to be coupled to an accessory for operation thereof;
• a sensing circuit configured to detect, during operation of the power tool, linear acceleration of the power tool along an axis;
• and
• a controller configured to:
• (a) receive a signal from the sensing circuit representing the linear acceleration of the power tool along the axis,
• (b) compare the linear acceleration to a predetermined threshold, and
• (c) in response to the linear acceleration satisfying the predetermined threshold, stopping the motor;
• wherein the linear acceleration along the axis is a first linear acceleration along a first axis and wherein the controller is configured to compare the linear acceleration to a predetermined threshold by:
• computing a sum of the first linear acceleration in the first axis, a second linear acceleration in a second axis, and a third linear acceleration in a third axis;
• and
• comparing the sum to a predetermined gravity value,
• wherein the controller is configured to stop the motor in response to the sum satisfying the predetermined gravity value.